1. Field of the Invention
The present invention relates generally to medical devices and methods. More particularly, the present invention relates to a balloon catheter having an exchangeable balloon structure.
Percutaneous transluminal angioplasty procedures have become a therapy of choice for treating stenosed regions in the patient""s vasculature, particularly the coronary vasculature. Recently, the use of such angioplasty procedures has often been combined with stent placement and/or radiation treatment to inhibit restenosis and hyperplasia following angioplasty. When performing such multiple, sequential treatments, it is usually necessary to xe2x80x9cexchangexe2x80x9d catheters which are used to perform each of the procedures. That is, the initial angioplasty treatment will be performed using a balloon angioplasty catheter. After the angioplasty is completed, a second catheter carrying a stent or other vascular prosthesis must then be introduced to the treatment site. Introduction of the second catheter involves first removing the balloon angioplasty catheter and then placing the second catheter in the treatment region. Optionally, a third catheter may then be exchanged for the second in order to perform radiation or other treatments in order to inhibit hyperplasia.
In performing such multiple, sequential treatments, most physicians prefer to leave a xe2x80x9cguidewirexe2x80x9d in place to the treatment location. A guidewire is a small diameter, highly flexible wire that can be steered to the target location through the vasculature and which then acts as a guide path for introducing and positioning the balloon angioplasty and other interventional catheters.
In the early days, balloon angioplasty catheters were designed to be introduced into the vasculature in an xe2x80x9cover-the-wirexe2x80x9d manner. That is, the catheters were designed to have passages, commonly referred to as guidewire lumens, which extended the entire distance from the distal end of the catheter to the proximal end of the catheter. The catheter could then be loaded over a proximal end of a guidewire which was already in place in the patient and then advanced over the guidewire until a distal end of the catheter reached the target site. While functional, the need to maintain control of the guidewire while the interventional catheter was being introduced meant that the guidewire had to have an excess length outside of the patient which was greater than the length of the catheter being introduced. If the length were any shorter, the treating physician would not be able to hold on to the guidewire as the catheter was being introduced. Although necessary for catheter introduction, the excess guidewire length (optionally in the form of a detachable extension) was very difficult to manage during other parts of the treatment.
To overcome the difficulties associated with very long guidewires xe2x80x9crapid exchangexe2x80x9d or xe2x80x9cmonorailxe2x80x9d balloon angioplasty catheters were developed. A number of specific designs have been developed over the years, and the rapid exchange catheters generally have a shortened guidewire lumen which extends from a distal tip of the catheter to an exit port located closer to the distal end of the catheter than to the proximal end. By reducing the length of the guidewire lumen, the need for a guidewire having excess length outside of the patient is also reduced.
The use of rapid exchange catheters has become wide spread, and they have proven to be particularly valuable for use as stent delivery catheters. Stent delivery catheters are normally used after an initial angioplasty treatment. In such cases, the angioplasty catheter will be removed and exchanged for the stent delivery catheter. Use of an angioplasty catheter having a rapid exchange design facilitates removal of the angioplasty catheter over short guidewires. Similarly, use of the stent delivery catheter having a rapid exchange design facilitates introduction of the catheter over the guidewire which remains in place in the patient.
Despite their widespread acceptance, rapid exchange catheters suffer from a number of limitations. In particular, the shortened guidewire lumens reduce the xe2x80x9cpushabilityxe2x80x9d of the rapid exchange catheters. The use of full length guidewire lumens as provided by the over-the-wire designs results in an overall increase in the column strength of the catheter being introduced. That is, the catheter derives column strength not only from the catheter body itself, but also from the guidewire which is in place in the guidewire lumen over the entire length of the catheter, allowing better access across tight lesions. Additionally, presence of the guidewire in a full length guidewire lumen lessens the risk of the catheter body kinking or collapsing in tortuous regions of the vasculature. Kinking can be a particular problem at the point where the guidewire exits a catheter body in a rapid exchange design.
The second problem associated with the use of rapid exchange catheters is the inability to exchange the guidewire. Guidewire exchange in over-the-wire catheters is quite simple since the guidewire lumen extends the full length of the catheter body. In rapid exchange catheters, in contrast, there is no guidewire lumen in the proximal portions of the angioplasty catheter. It is therefore difficult to reintroduce a guidewire into the shortened guidewire lumen of the rapid exchange catheter.
For these reasons, it would be desirable to provide improved apparatus, methods, and kits which permit the exchange of catheters and catheter components over shortened guidewires. Particularly, it would be desirable to provide improved balloon angioplasty and other catheters which can be introduced to the vasculature in the manner of an over-the-wire catheter, but which allow removal of the catheter over a shortened guidewire and/or which permits exchange of catheter components over the catheter body which remains in place over the guidewire. It would be further desirable to provide balloon catheters and methods for their use which permit exchange of balloon structures over the catheter body while the catheter body remains in place in the vasculature over a guidewire and where the replacement balloon structure may optionally carry a stent. At least some of these objectives will be met by the invention described in claims herein after.
2. Description of the Background Art
Rapid exchange catheters having guidewire exchange devices are described in U.S. Pat. Nos. 5,281,203; 5,571,094; and 5,919,175. Sleeves for positioning stents, drug infusion tubes, imaging transducers, and other interventional devices over balloon angioplasty catheters are described in U.S. Pat. Nos. 5,776,191; 5,810,869; and PCT Publication W097/07756. Rapid exchange and related catheters are described in U.S. Pat. Nos. 6,056,722; 6,007,517; 5,980,4861; 5,947,927; 5,921,971; 5,919,164; 5,891,056; 5,846,246; 5,833,659; 5,830,227; 5,827,241; 5,807,355; 5,814,061; 5,769,868; 5,855,685; 5,749,888; 5,738,667; 5,728,067; 5,709,658; 5,685,312; 5,626,600; 5,620,417; 5,607,406; 5,554,118; 5,545,134; 5,531,690; 5,501,227; 5,472,425; 5,468,225; 5,460,185; 5,458,613; 5,451,223; 5,413,559; 5,395,335; 5,383,853; 5,364,376; 5,350,395; 5,346,505; 5,336,184; 5,334,147; 5,328,472; 5,300,085; 5,380,283; 5,263,963; 5,232,445; 5,195,978; 5,135,535; 5,061,273; 5,040,548; 4,762,129; 4,988,356; 4,947,864; 4,748,982; and WO 99/13935.
The present invention provides improved intravascular balloon catheters and methods for their use. The catheters are suitable for use for the treatment of a variety of conditions within different locations of a patient""s vasculature. In particular, the catheters can be used in the coronary, peripheral, and cerebral regions of a patient""s vasculature for virtually any treatment modality that relies on balloon expansion, particulaty angioplasty, stent placement, and the like.
Intravascular balloon catheters according to present invention comprise a tubular catheter body having a proximal end, a distal end, and a guidewire lumen extending therebetween. Usually, the guidewire lumen will extend the entire distance from the proximal end to the distal end of the catheter, although in some instances the guidewire lumen could be shortened (in manner of a conventional rapid exchange catheter), could be split to facilitate removal of the guidewire, and/or could be provided with a breakaway feature which allows opening the guidewire lumen to facilitate guidewire removal. In all cases, the intravascular balloon catheters of the present invention will further comprise a balloon structure having a passage which is slidably receivable over the tubular catheter body. Thus, the balloon structure can be selectively introduced and removed over the tubular catheter body to permit exchange of the balloon structure with another balloon structure (or in some cases a non-balloon structure) either before or during performance of an intravascular interventional procedure employing the balloon.
Usually, the balloon structure will comprise an inflatable component, e.g. a balloon, having an inflation tube extending proximally from the balloon when the balloon is disposed near the distal end of the tubular catheter body. Conveniently, the inflation tube can also be used to manipulate the balloon structure. That is, the balloon structure can be advanced and withdrawn over the tubular catheter body by pushing and pulling on a proximal end of the inflation tube while the tubular catheter body remains in place. In such cases, the inflation tube will have sufficient column strength to advance and retract the balloon structure over the tubular catheter body. Usually, it will be in the form of a hypotube, but other structures would also be possible. Alternatively, a separate manipulation shaft could be attached to the balloon structure with a separate inflation structure, either attached directly to the balloon structure or optionally provided in the tubular catheter body. In the later case, the tubular catheter body will include an inflation lumen and the balloon structure will include an inflation port which mates with the inflation lumen in order to permit inflation of the balloon through the tubular catheter body. A separate manipulation shaft will then be provided on the balloon structure extending proximally from the balloon structure when the balloon is disposed near the distal end of the tubular catheter body.
The inflatable structure, in an exemplary embodiment, will comprise a balloon attached to an inner sleeve, where the inner sleeve has an axial passage which removably receives the tubular catheter body. Usually, the inner sleeve will be longer than the balloon structure, with the inner sleeve usually having a length in the range from 3 cm to 50 cm, usually from 4 cm to 40 cm, and typically from 5 cm to 25 cm. The balloon or other inflatable structure (or in some cases other radially expansible structure) will be much shorter, typically being in the range from 1 cm to 5 cm, usually from 2 cm to 4 cm. The inner sleeve may be formed from conventional catheter materials, typically being an extruded polymer tube.
When an inflation tube is attached to the balloon structure, the tubular catheter body will preferably be free from structure which interferes with introduction of the balloon structure over the proximal end of the tubular catheter body. Optionally, a hemomostatis structure may be provided within the proximal end of the guidewire lumen, but the hemomostatis structure will not add to the profile of or otherwise affect the catheter body such that it would interfere with loading of the balloon structure. Alternatively, a removable hub could be provided, but upon removal of the hub, the proximal end of tubular catheter body should be sufficiently free of protruding structure to permit introduction of the balloon structure thereover. When the inflation lumen is provided within the tubular catheter body, it will be usually be necessary to provide a removable hub at the proximal end of the catheter body to permit inflation of the balloon through a port on the hub.
The intravascular balloon catheters of the present invention will include at least a first balloon structure having the properties described above. Usually, the first balloon structure will be preloaded over the tubular catheter body, and the assembly sterilized and packaged as a complete unit. Optionally, a second balloon structure having a passage which is slidably receivable over the tubular catheter body may be also provided. The second balloon structure may be included as part of a single system together with the first balloon structure and tubular catheter body, usually being packaged together in a sterile manner with the other system components. Typically, the second balloon structure will differ from the first in someway, such as the dimensions, including diameter, length, or both; shape; balloon material; balloon characteristics, such as compliance, flexibility, elasticity or the like; or other feature. In a particular example, the second balloon structure may carry a stent or other vascular prosthesis, where the first balloon structure is intended for performing angioplasty or other therapeutic or diagnostic procedure, and the second balloon structure is intended to deliver a stent after the angioplasty treatment. Other examples include drug infusion balloons, radioactive delivery balloons, atherectomy, and the like. Of course, the intravascular balloon catheters including only a single balloon structure may also be adapted to carry a stent, drug infusion balloon, radioactive delivery balloon, or the like, as well.
Methods according to the present invention for balloon exchange over a tubular catheter body comprise withdrawing a balloon structure coaxially over the tubular catheter body while the tubular catheter body remains in place over a guidewire in a blood vessel. The balloon structure is withdrawn proximally, usually so that it may be removed over a proximal end of the tubular end of the catheter body. After withdrawing a first balloon structure, a second balloon structure is introduced over the tubular catheter body in distal direction while the tubular catheter body remains in place over the guidewire. Typically, the second balloon structure will be introduced over the proximal end of the tubular catheter body. A particular advantage of the these methods is that the first balloon structure and tubular catheter body maybe introduced over a short guidewire (i.e. one that is only slightly longer than the angioplasty catheter itself e.g. 10 cm to 35 cm) in the manner of an over-the-wire angioplasty catheter. After the balloon catheter assembly is in place, however, the first balloon structure may be withdrawn from over the proximal end of the tubular catheter body and exchanged for a second (subsequent) balloon structure. As the balloon structures themselves will be shorter than the catheter body, typically being from 3 cm to 50 cm, they can be withdrawn without losing manual access to the proximal ends of the tubular catheter body and short guidewire.
In an exemplary protocol using the intravascular balloon catheters and methods of the present invention, the balloon catheter comprising a first balloon structure pre-loaded over a tubular catheter body is first introduced together with a guidewire to a target region in the vasculature in a conventional manner. Usually, a distal end of the guidewire, extends beyond the distal end of the tubular catheter body by a short distance as the balloon catheter assembly is being advanced. In that way, a short guidewire can be used where the guidewire is fully supported in the guidewire lumen of the tubular catheter body, which typically runs the entire length of the catheter body.
After the first balloon structure has been positioned at the target location within the vasculature, e.g. a stenosed region within the coronary vasculature, the first balloon may be expanded to treat the target region, e.g. by opening the stenosed region. Thus, the first balloon structure may act as angioplasty balloon, with the balloon being substantially non-distensable at the relatively high inflation pressure is used, typically from 3 atmospheres to 20 atmospheres. Alternatively, the first balloon could be any other therapeutic or diagnostic-type of balloon.
After the initial balloon treatment is completed, the balloon structure may be withdrawn proximally from over the tubular catheter body. This may be accomplished by using the inflation tube when the balloon structure includes such an inflation tube. Otherwise, withdrawal will be typically be accomplished using a shaft, such as a solid core wire or hypotube attached to the balloon structure and extending proximally therefrom. The passage of the balloon structure, as described above, will usually be relatively short so that the balloon structure may be withdrawn from over the proximal end of the tubular catheter body and guidewire, with the lengths of the tubular catheter body and guidewire being extended a small amount to allow manual access while the balloon structure is being withdrawn thereover.
After the first balloon structure has been withdrawn, the second balloon structure may be introduced over the proximal ends of both the guidewire and the tubular catheter body. Again, the length of the passage in the second balloon structure will typically be in the range from about 3 cm to 50 cm, so that manual access to both the tubular catheter body and guidewire will remain at all times. The second balloon structure may be advanced using either an inflation tube or other manipulation shaft overextending proximally from the balloon structure. The balloon structure will then be advanced until it reaches a location near the distal end of the tubular catheter body where it can be further positioned within the treatment region. In the exemplary case, the second balloon structure will carry a balloon expandable stent or other vascular prosthesis, where the stent is implanted by expansion of the second balloon structure, Optionally, further treatments can be provided, e.g. using a third coaxial sleeve structure which could carry drugs, genes, radiation, or other therapeutic agents or modalities. The third coaxial structure may, but need not, also comprise an inflatable balloon. The third structure usually will be introduced in a manner analogous to the introduction of the second balloon structure, as just described. There, of course, could be fourth, fifth, and even more treatment steps performed by successively introducing balloon, sleeve, and other structures over the tubular catheter body. Moreover, it will also be possible to introduce two or more balloon structures over the tubular catheter body at the same time.
After the patient treatment is completed, the intravasculature catheter structure which remains over the guidewire will be withdrawn. In a first option, the catheter and guidewire can be withdrawn simultaneously where the catheter is never in the vasculature without the guidewire present in the guidewire lumen. Alternatively, the balloon or other coaxial sleeve structure can be withdrawn from over the tubular catheter body prior to removing the tubular catheter body and guidewire simultaneously. As a third option, the tubular catheter body could be provided with an axial slit or break away portion to permit removal of the tubular catheter body from over the guidewire with the guidewire remaining in place. In that way the guidewire would remain in place for subsequent use with other catheters or devices.